title: A volumetric-modulated arc therapy using sub-conformal dynamic arc with a monotonic dynamic multileaf collimator modulation.
abstract: We present a new dose delivery scheme utilizing sub-conformal dynamic arc (sub-CD-ARC) with a dynamic multileaf collimator (dMLC) modulation in a single rotation. In sub-conformal delivery, a MLC aperture conforms not to the whole target but to its portion, simultaneously completely avoiding organs at risk (OARs). In CD-ARC therapy, the dose deposition level depends on the target width and distance to the axis of rotation, and therefore the use of multiple arcs is necessary to achieve a uniform dose within the target in 3D. In our delivery scheme, the dose deposition variations symptomatic of non-modulating sub-CD-ARC are compensated for in 3D by a quasi-periodic monotonic dMLC modulation. For this reason, we call this scheme sub-conformal dynamic modulated arc (sub-CD-MARC) therapy. The advantage of using such a modulation is that MLC leaf motion has just a few control points, and that an inverse planning problem is reduced to a linear equation problem with a few unknown parameters, which have clear physical meaning. We show the general dosimetric properties of sub-CD-ARC and sub-CD-MARC for a specific geometry of the target and OARs (rotational symmetry with varying inner and outer radii along the axis of rotation). In addition, we present numerical results of sub-CD-MARC inverse planning optimization.
authors.affiliation: Department of Radiation Oncology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA. pzygmanski@LROC.havard.edu
authors.forename: Piotr
authors.initials: P
authors.lastname: Zygmanski
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Högele
authors.forename: Robert
authors.initials: R
authors.lastname: Cormack
authors.forename: Lee
authors.initials: L
authors.lastname: Chin
authors.forename: Rainer
authors.initials: R
authors.lastname: Löschel
mesh_terms: D006801:Humans; D008297:Male; D011467:Prostate / Q000528:radiation effects; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D012399:Rotation